Sensorless strain-bounded grasping of fruit
Yusei Shuto, Danilo Vasconcellos Vargas
原文摘要
Robotic post-harvest handling must hold produce without bruising it, yet fruit stiffness varies several-fold with ripeness, so no fixed grip force suits every item. We instead bound compression strain using only the encoder and motor effort of a servo gripper. Given a strain bound $\varepsilon$ and a stiffness floor $k_{\min}$ set once per crop and gripper, the controller estimates object size $\hat{D}$ at contact, refines stiffness $\hat{k}$ conservatively by probing, and stops at $\hat{F} = \varepsilon \hat{k} \hat{D}$, keeping true strain below $\varepsilon$ with high probability above a quantified contact-detection floor. In simulation, where fixed force thresholds either drop heavy objects or damage soft ones, the proposed controller carries 92% of objects within its operating range with 0.3% damage. On cherry and medium tomatoes, setting $\varepsilon$ above the detection floor scaled the stop force threefold across fruit sizes, carrying all fruits while reducing markings on cherry tomatoes from 8/10 to 1/10; on medium tomatoes both marked 3/6.
cs.RO